This invention relates to a multi-port valve that is used for selection of fluid streams and/or injection of fluids in processes such as liquid chromatography. In particular, the invention relates to an injection/selection valve that utilizes a ferrule cluster to connect tubes or capillaries to a common port in the valve.
Multiport selector/injector valves are well known and have been used in a variety of industrial processes, such as liquid chromatography. For example, selection valves are commonly used in liquid chromatography and other analytical methods to direct fluid flow along alternate paths. Such valves are also used to terminate fluid withdrawal from one source and select another source of fluid, for example, such as when a variety of streams in an industrial process is selectively sampled for analysis.
Injector/selector valves are often used in high pressure liquid chromatography (HPLC) or gas chromatography (GC). U.S. Pat. No. 4,242,909 (Gundelfinger '909), which is hereby fully incorporated by reference, describes a sample injection apparatus for withdrawing liquid samples from vials and injecting them into a chromatographic column or other analyzing device. The apparatus is said to minimize wastage, cross contamination, and dilution of the samples, and to be capable of automation with a minimum of complexity. Injector/selector valves are particularly useful in chromatographic applications since a substantial amount of time and effort is required to set up a particular HPLC or GC system, which may often utilize multiple columns and/or multiple detection systems. Multiport selection valves permit the operator of the chromatograph to redirect flows such that particular samples are selected for injection into a particular column, or alternatively, to direct the output from a particular column to one or more different detectors.
As mentioned above, multiport selection valves have been known for some time, including those which utilize a cylindrical rotor and stator combination. In some of these valves, the stator holds the fluid tubes in fixed relation to each other and presents the tube ends to a rotor face which may contain a grooved surface. By varying the angle of the rotor, the tubes are selectively brought into fluid communication. One type of injector/selector valve using a rotor/stator combination is the Type 50 rotary valve from Rheodyne, Incorporated. The Type 50 valves are said to operate by rotation of a flat rotor against a flat stator (see “Operating Instructions for Type 50 Teflon Rotary Valves,” Rheodyne, Incorporated, printed in U.S.A. 4/94). Another rotor/stator selector valve is shown in U.S. Pat. No. 5,193,581 (Shiroto, et al.). The valve is said to comprise, among other things, a stator plate having a plurality of outlet holes extending through the stator plate and arranged in a circle concentric with a valve casing, and a rotor having a U-shaped passage formed in the rotor. The rotor is said to be rotated through a desired angle so that an inlet hole can be in fluid communication with selected ones of the outlet holes through the U-shaped passage of the rotor.
U.S. Pat. No. 5,419,419 (Macpherson) describes a rotary selector valve that is used in connection with an automatic transmission in an automobile. A motor is said to index a shear plate of the selector valve to predetermined positions for shifting the transmission. A series of working lines as shown in
U.S. Pat. No. 3,494,175 (Cusick, et al.) discloses a valve having a plurality of capillaries which are held in spaced relationship within a manifold plate member. U.S. Pat. No. 3,752,167 (Makabe) discloses a fluid switching device including a plurality of capillaries that are held within threaded holes by couplings. A rotary member allows fluid communication between the tubes. U.S. Pat. No. 3,868,970 (Ayers, et al.) discloses a multipositional selector valve said to be adapted with a means for attaching a plurality of chromatographic columns to the valve, such that the flow can be directed into any of the columns. U.S. Pat. No. 4,705,627 (Miwa, et al.) discloses a rotary valve said to consist of two stator discs and a rotor disposed between the two stator discs. Each time the rotor is turned intermittently it is said, different passages are formed through which the fluid in the valve runs. U.S. Pat. No. 4,722,830 (Urie, et al.) discloses multiport valves. The multiport valves are said to be used in extracting fluid samples from sample loops connected with various process streams.
In many applications using selector/injector valves to direct fluid flows, and in particular in liquid and gas chromatography, the volume of fluids is small. This is particularly true when liquid or gas chromatography is being used as an analytical method as opposed to a preparative method. Such methods often use capillary columns and are generally referred to as capillary chromatography. In capillary chromatography, both gas phase and liquid phase, it is often desired to minimize the internal volume of the selector or injector valve. One reason for this is that a valve having a large volume will contain a relatively large volume of liquid, and when a sample is injected into the valve the sample will be diluted, decreasing the resolution and sensitivity of the analytical method.
In the design of selector or injector valves with minimal internal volume, the prime design consideration is to bring all of the fluid passages into the closest possible proximity to each other. To do this with conventional capillary connectors is very difficult, since the nuts of the connectors are relatively large and require a fair amount of space. Thus, the valve itself has to be relatively large in order to accommodate the connections.
One solution to the large connectors has been to drill the injector ports on an angle. By angling the injector ports, the ends of the channels can all emerge in close proximity to a common point, while the opposite ends of the channels are sufficiently spaced apart to accommodate the larger connectors. An example of this approach is shown in U.S. Pat. No. 5,419,208 (Schick), which is hereby fully incorporated by reference. However, this approach has certain drawbacks. First, angled holes are difficult to produce and expensive to machine. Further, the angled passage from the capillary connector to the center of the valve stator is longer than it would be if the capillary could be connected directly on the face of the valve in close proximity to other capillaries. This additional length creates additional dead volume, which is undesirable as noted above. A further disadvantage of this approach is that the emerging hole near the center of the valve stator has an elliptical shape, which is not desirable.
Another type of capillary connection is shown in U.S. Pat. No. 4,792,396 (Gundelfinger '396), which is hereby fully incorporated by reference. Gundelfinger '396 describes a frame used as part of an injector said to be useful in loading a sample at high pressure into a chromatographic column. The frame is said to comprise ferrules for sealing tubes, and it is said that a tube coupling hole in the frame can couple to a standard {fraction (1/16)}″ tube, but also can couple to a much smaller diameter tube useful for minimizing dispersion when small samples or small chromatographic columns are used. The use of ferrules to make capillary or tubing connections to chromatography apparatus is also shown in, for example, U.S. Pat. Nos. 5,674,388 (Anahara), 5,744,100 (Krstanovic), 5,472,598 (Schick), 5,482,628 (Schick), and 5,366,620 (Schick).
It would be desirable to have a selector/injector valve that can be made with the smallest possible valve volume. There is also a need for an injector/ selector valve which brings capillary or tube ends into the closest possible proximity to each other and to the valve stator so that valve dead volume is minimized. Finally, there is also a need for a capillary connector system that can be used to connect capillaries in the closest possible proximity.
The invention relates to a multi-port injection/selection valve that utilizes one or more ferrule clusters to connect tubes or capillaries to a common port in the valve. The ferrule clusters connect the tubes or capillaries to the body of the valve assembly. The use of ferrule clusters, as opposed to conventional connectors such as nuts and/or bolts, permits the capillary ends to be positioned in extremely close proximity to the valve rotor and to each other, thus minimizing the space between two capillaries when they are in brought into fluid communication with each other (i.e., the “dead volume” in the connection). The ferrule clusters can be made extremely small.
In one embodiment the invention is a valve, comprising: a) a plurality of ferrules formed into one or more ferrule clusters, each of said ferrules having a ferrule through-hole; b) a stator in contact with at least one of said ferrule clusters, said stator having a stator front side and a stator flat surface opposite said front side, said stator front side having a plurality of impressions into which some or all of said ferrules are received, each of said impressions opening to a terminal cylindrical bore (tube pocket), each of said impressions also having a stator through-hole opening onto said stator flat surface; c) a plurality of capillary tubes, each of said capillary tubes extending through at least one of said ferrule through-holes and into a stator impression up to the terminus of said cylindrical bore; d) means for applying pressure to said one or more ferrule clusters; and e) a rotor comprising a stator-contact surface and a fluid communication channel, said stator-contact surface abutting said stator flat surface and being rotatable about an axis to establish fluid communication between selected pairs of capillaries through said fluid communication channel.
In yet other embodiments, the invention is a capillary chromatographic system comprising the valve of the invention. In still other embodiments the invention is a method for carrying out a chromatographic analysis and a method for connecting capillary tubes to a chromatographic system.
FIG.
As seen in
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The inventive valve comprises one double-ended ferrule cluster or one or more single-ended ferrule clusters. When two or more single-ended ferrule clusters are employed, they are preferably arranged in a “stacked” configuration. Referring again to
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The rotor shown in
While the rotors shown in FIG.
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Whether double-ended or single-ended ferrules are used, the individual ferrules, including the single central ferrule if present, are preferably joined together as part of an integral, one-piece ferrule cluster. That is, the ferrule cluster is a one-piece cluster that is not adapted to be disassembled into multiple pieces. Such one-piece clusters can be formed, for example, by compression molding of plastic materials to form a plastic part, or by machining a piece of solid bar stock. Alternatively, an integral ferrule cluster as defined herein could be formed by fusing, gluing, soldering, welding, or using like operations to join multiple pieces of material to form a single part. Referring again to
While the specific embodiments of the inventive valve shown in FIG.
The ferrule clusters may be fabricated form any suitable material, including thermoset materials and thermoplastics. Polyether-ether ketone (PEEK) is a particularly suitable thermoplastic material for fabricating the ferrule clusters of the invention. The rotor and stator of the inventive valve may be fabricated from any suitable material, for example, metal, plastic materials, ceramic materials, or zirconia. In a preferred embodiment, the rotor and stator are ceramic or zirconia.
The valve of the instant invention may be fabricated to any useful size. However, the inventive valve is particularly useful in micro applications, in particular those utilizing fluid flow rates of 0.5 ml/min or less. Typically this includes capillary chromatography. As used herein, and for the purpose of interpreting the claims of this patent specification, the terms “capillary chromatographic system” and “capillary chromatography” shall be understood to refer to a chromatograph, or chromatographic analyses performed thereon, respectively, which employ(s) one or more capillary columns. As used herein, “capillary column” means a capillary (capillary tube) having a length greater than or equal to 25 meters, wherein the capillary has an outside diameter from about 50 to about 1600 microns. It will be understood that the capillaries which may be connected to the inventive valve need not be “capillary columns,” although they may be. For example, some of the capillaries may be shorter capillaries which are used to feed or transfer fluids to a capillary column. Those skilled in the art will understand that the term “chromatographic analysis” refers not only to the separation or partial separation of mixtures into their individual components, but also to methods in which a single, pure material is analyzed. In the latter situation, it may technically be the case that no “separation” occurs, because only a single, pure component is present. Further, as noted above a distinction is sometimes made between chromatographic methods which are performed for analytical purposes and those which are performed for preparative purposes. However, for convenience, the term “chromatographic analysis” as used herein will be understood to include separations and methods which are conducted for both analytical and preparative purposes.
Capillary chromatography has long been known for extremely high resolution, and it can be carried out using both gas and liquid mobile phases. In this sense the term “fluid” will be understood, as it normally is,. to include both liquids and gases. The valve of the present invention is also useful in high pressure liquid chromatographic (HPLC) applications, including capillary HPLC. Thus, one embodiment of the invention is a capillary chromatographic system, including gas chromatographs and liquid chromatographs, comprising the valve of the invention.
While the inventive valve and its components may be sized in any useful manner, certain valve and valve component dimensions are preferred. Referring to FIG.
In another embodiment of the invention, the capillaries
In yet another embodiment, the present invention is a method for carrying out a chromatographic analysis, comprising: a) providing a plurality of ferrules formed into one or more ferrule clusters, each of said ferrules having a ferrule through-hole; b) placing a stator in contact with at least one of said ferrule clusters, said stator having a stator front side and a stator flat surface opposite said front side, said stator front side having a plurality of impressions into which some or all of said ferrules are received, each of said impressions opening to a tube pocket, each of said impressions also having a stator through-hole opening onto said stator flat surface; c) disposing a plurality of capillary tubes through said ferrule through-holes and into said tube pockets; d) applying pressure to said one or more ferrule clusters; e) placing in contact with said stator a rotor comprising a stator-contact surface and a fluid communication channel such that said stator-contact surface abuts said stator flat surface and is rotatable about an axis to establish fluid communication between selected pairs of capillaries through said fluid communication channel; f) placing one or more of said capillaries in fluid communication with a capillary column; g) rotating said rotor to establish fluid communication between said capillary column and one or more of said capillaries; and h) passing a fluid through one or more of said capillaries and into said capillary column. In yet a further embodiment, the present invention is an automated method or automated chromatographic system for carrying out a chromatographic analysis using the valve of the invention.
In still another embodiment, the present invention is a method for connecting capillaries to a chromatographic system, the method comprising: a) providing a plurality of ferrules formed into one or more ferrule clusters, each of said ferrules having a ferrule through-hole; b) disposing a plurality of capillary tubes through said ferrule through-holes; c) providing a plurality of impressions into which said some or all of ferrules are received, each of said impressions having a tube pocket into which one of said capillary tubes extends; and d) applying pressure to said one or more ferrule clusters.
While the present invention has been shown and described in its preferred embodiment and in certain specific alternative embodiments, those skilled in the art will recognize from the foregoing discussion that various changes, modifications, and variations may be made thereto without departing from the spirit and scope of the invention as set forth in the claims. Hence, the embodiment and specific dimensions, materials and the like are merely illustrative and do not limit the scope of the invention or the claims herein.